Many systems require the dispensement of additives into the primary fluid flow in order to alter the characteristics of she resulting solution. For example, in the residential arena it is desirable to be able to inject such additives as pesticides, fertilizer, detergent, etc., depending upon the application, into a water line. In the firefighting industry it is advantageous to be able to inject foam concentrates into a water line to aid in the suppression or extinguishment of fire.
One type of household sprayer is the garden sprayer which is based upon the venturi principle. This type of sprayer is used to apply pesticides and/or fertilizers to lawns and gardens. It is comprised of an inlet hose connection, a venturi device, an additive source, and a discharge nozzle. This type of device may be referred to as an atmospheric eductor. This means that the additive is at atmospheric pressure. In principle high pressure water (Between 40 to 75 psi, for most residential systems) enters through the inlet connection. The water then passes through a venturi jet. The venturi jet is a conical or tapered shape, in its most efficient design. The water is forced to pass through a smaller tapered area. In order to do so, the velocity of the water increases. This increase in velocity causes the water pressure to drop. When the water pressure drops below zero gauge a low-pressure zone is created (i.e. Vacuum). The additive is “sucked” into this low-pressure zone by atmospheric pressure where it mixes with the incoming “drive” water. Those skilled in the art often refer to this as an eductor. The solution (drive water plus additive) then travels to the discharge nozzle and exits. This type of system typically experiences a permanent pressure loss of 30 to 40%. Since nozzle range is dependent upon pressure, this results in poor performance and range of the discharge. The lawn and garden hand nozzles have superior range and discharge pattern when compared to a sprayer, provided water pressure is adequate. This is due to the greater energy, or pressure, being available to the nozzle. Because of the sprayer pressure limitations, a conventional nozzle cannot be connected to the sprayer, it would not pick-up additive. The present invention discloses an additive supply system that represents a negligible (approximately 10%) pressure loss and allows the operator to employ conventional “End of Line Devices” (EOLD) such as those discussed herein. These devices have superior reach and effectiveness. This system can be located anywhere in the water hose line and has the additional potential benefit of relieving the operator from the burden of carrying the “additive container”.
Additionally, this type of system (garden sprayer) is essentially designed around one target flow rate. Therefore, the rate of additive flow is relatively constant. If the drive water flow rate is lower (due to lower available water pressure) the proportioning may be rich since the amount of additive remains nearly constant. If the flow rate is above the design point (available water pressure is high), the system will be lean due to the increase in drive water (the proportioning rate will be low). Hence this type of device will not accurately proportion and therefore has a limited operating flow range. The present invention will maintain a nearly constant proportioning rate across the entire design flow range.
Since water is the primary fluid used in firefighting, it is often advantageous to employ water driven mechanisms that can supply foam concentrate into the primary water line. Numerous mechanisms exist in the firefighting industry that are designed to add foam concentrate to the waterline, but not all are water powered. Some of these systems are portable, while others are mounted in mobile equipment or are designed as a fixed installation. Many of these systems feature some type of metering control that allows the percent of concentrate entering the waterline to be controlled from 0 to 6%. The most common and basic of the portable mechanisms are eductors. An example of this type of apparatus would be the model 241-60 from Elkhart Brass Manufacturing Company. These type devices utilize the venturi principle similar to the design mentioned above. A foam source is connected to the suction port typically via a metering valve. These devices are relatively inexpensive, and are water driven, but they have a set flow rate, and they create a permanent pressure loss of 30 to 40% as mentioned above. Because of this, they require a higher inlet pressure to compensate for this pressure loss and they are very sensitive to the amount of pressure that can be downstream of the eductor. If the wrong nozzle (or EOLD), or too much hose, or too small a hose diameter is connected between the nozzle and the eductor, performance will suffer and it may stop picking up additive/foam altogether.
Many of the more sophisticated firefighting foam systems on the market utilize a foam pump to raise the foam pressure of the team concentrate so that it can be infected into the water line. These pumped foam systems all use fixed displacement pumps to pump the concentrate. Fixed displacement pumps have good volumetric efficiency characteristics with very flat pressure-to-flow performance curves, which make them the pump of choice for foam system manufactures. Since fixed displacement pumps displace a fixed volume per revolution, the desired discharge flow rate must be controlled by one of two ways: control the input speed to match demand or have no speed control and divert the excess.
Numerous schemes exist on the market for controlling the input speed. The relatively small systems typically rely on electric motors with electronic speed controls. An example of this type of system would be the FoamLogix System manufactured by Hale Products in Conshohocken Pa. The larger systems typically employ a hydraulic transmission with electronic controls to control the pump speed and thus the output flow rate. An example of this type of system is the Servo Command System manufactured by National Foam in Exton Pa. These systems can handle broad pressure and flow ranges, have little to moderate pressure loss (typically ranging from 5 to 10%), and are not sensitive to back pressure. However, they all require a dedicated drive source (electric, hydraulic, engine, etc.) and are not driven by the flow of the primary fluid, which for firefighting purposes is generally water. These systems tend to cost more, require more maintenance, are more complex, and less reliable. The present invention accomplishes the same feats by varying the pump speed proportionally to the flow rate. In addition, the present invention is less complicated thereby improving reliability and reducing cost.
Systems that employ a fixed displacement pump and divert the excess flow to the suction side of the pump or back to the foam tank are known as “bypass” type systems. Control for these systems may be mechanical, electric, or a combination of the two. An example of this latter type would be the Feecon Balance Pressure Foam System manufactured by Kidde-Fire in Exton Pa. These systems can also handle a broad pressure and flow range, have moderate pressure loss (typically ranging from 5 to 10%), and are not sensitive to back pressure. They usually consist of a direct drive arrangement, where the drive, or power source, is connected directly to the foam pump. Therefore the drive system is usually simple compared to their speed controlled counterparts. However, like the speed controlled systems mentioned above, they all require a dedicated drive source and are not portable and are still subject to increased cost, maintenance, complexity, with less reliability. In addition these systems are less efficient since they create excess foam that most then be dumped back to a tank or to the pump suction. This comprises a waste of energy. The present invention offers the same broad choice of capabilities (proportioning rates and pressure/flow ranges) without the wasted energy or complicated drive and control systems.
Another type of system on the market is that of a water motor that is coupled to a foam pump. An example of this type of system is the FireDos system marketed by ThermoGel. This system is completely water powered. It uses a fixed displacement water motor to torn a fixed displacement foam pump. This system may be portable and water driven like the eductor, but it is not sensitive to downstream pressure and it can handle a broader operating range. It is not as complicated, and does not require a separate source of power like the other pumped systems. However, it uses a fixed displacement foam pump and therefore suffers the same drawbacks as the bypass type pump systems mentioned above. In addition, the controls for divesting the excess foam, along with the pump and motor combination being joined via a coupling, make for a bulky arrangement. The present design has all the positive features of this device, but utilizes a variable displacement additive pump which makes for a more efficient design since no foam is bypassed. This results in less pressure loss in the system and snore pressure available to do positive work, such as improved nozzle range. One method employed in the FireDos system to select the proportioning rate is to employ a multi-piston positive fixed-displacement pump. This only allows for discrete step-wise rate selections. For example a pump may feature three cylinders. In operation one or two of the cylinders could be diverted to bypass foam back to the suction side. For example this may allow foam proportioning rate selection of 1% (two cylinders diverted), 2% (one cylinder diverted), or 3% (no cylinders diverted). The present invention offers a further advantage in that the proportioning rate is not step wise and can be infinitely varied between 0 and 3% for example.
A snore recent player in the foam market is Matte Maskin of Norway also marketed by INNOVFOAM. Matte Maskin uses a reaction type turbine to turn a fixed displacement foam pump. Turbines, like centrifugal pumps, suffer from a condition known as slip. This means that the proportioning will be greatly affected by the operating pressure and or the foam demand. Therefore, these systems have a narrow pressure operating range and typically operate at one fixed foam % setting.